How to reproduce:
1. Create a new project or open an existing one
2. Build and run the project
2. Open Player Settings (Edit -> Project Settings - > Player)
3. Change the Product Name value in the Player Settings
4. Build and run the project

Expected result: The name of the build executable file is the same as the product name
Actual result: The name of the build stays the same as the old product name

Reproducible with: 2018.4.16f1, 2019.3.0f6, 2020.1.0a21

Notes:
The issue does not reproduce on Unity 2017.4, as the executable name is chosen when building instead of being the same as product name.
The issue is only reproducible when selecting "Build And Run".
A possible workaround is to delete the Library folder, this way the name will change on new builds.